Manufacture of hydroxy carbazoles



Patented D. 1, 1931 g FRITZ BALLAUE' AND ALBERT SGHMELZER, F nniznrtrnrinyqnnfinnyi nssmnoas To me, or NEWAYORK, 11. 2., A CORPORATION oE'nEnA- GENERAL ANILINE worms, WARE MANUFACTURE or HYDROXY cAEEAzo Es" No Drawing. Application'filed' July 19, 1930, Serial'No. 469,278, and' in Germany Tune-29, 1929. i

The present invention relates to the production of hydroxy carbazoles and more particularly it relates to a process for preparing 2- or 3-hydroxy-carbazole from the corre sponding 2- or 3 alkoxy-tetrahydro-carbazole'. According to the ,present inventiona com-.

pound of the general formula: I

wherein O.alk stands for an alkoxy group which stands in the 2- or 3- p0sitionis heated in the presence of at least the calculated quantity of lead oxide at. a temperature of 400-600 C. until a gas consisting probably of a mixture of carbon dioxide and Watersteam no longer escapes from the reaction mixture.

As starting materials for performing the present invention the following compounds among others may be used:

Our invention is'illustrated by the follow ing example without being restricted thereto:

Example:

IIIiXGd'With'ZO parts by Weight otlead oxide and introduced into a glass tube. The remainder of the tube-is then 'filled'with lead oxide-pumice stone particles; The glass tube is placed in a brass tube or in a tube of fireclay in order to ensure a uniform heating. The distillation is then carried (out in-the manner usual for thisreaction, that to say example; carbon dioxide or nitrogen. The

identical -with,the methoxy carbazole' de-' scribed in theliterature. j r 'In an analogous mannerQ-hydrbxy-carba-Q 20 parts by weight of .ar-G- methoxy-tetrahydro-ca-rbazole are intimately the 'lead oxide-pumice stone mixture present is first wellheated and then the substance is rapidlydistilled over the lead oxide, advantageously in a current of inert, gas, such as for yield ofjthe crude productis good. By re- 1 crystalliz ing from xylene, 3-hydroxy-carba qzole is obtained in white needles of the melting point 256 C, Itis' identical in every respect with the. 3 -hydroxy-carbazole described in the literature. The 3-methoxycarbazole obtained therefromby methylation according to the customary methods crystal-1 lizes from alcohol in white needles of the melting point 1429 C. This is likewise zolecan alsobe obtained from the'2-"ethoxy-v tetrahydrocarbazole.

We claim: 7 f I 1 V .1., Process for preparing acompound of the general formula:

wherein-the hydroxygroup stands in .2- or .3-position which comprises-heating to a temperature of l00600 C. a tetrahydrocarbazole compound of the general formula: V

wherein stands for-an alkoxy group which. stands-in the 2- or 3-position in presence of at least the calculated quantity of lead oxide until a gasconsisting probably of carbon dioxide and wateresteam no longer escapes from the reaction mixture. 7

2. Process for preparing 3-hydroxy-carba zolewhich comprises heating a 3 -alkoxy- 5 .tetra-hydro-carbazole at a temperature of 400600 C. in the presence of at least the I calculated quantity of lead oxide until a.v gas consisting probably of carbon dioxide and ,water-steam no longer escapes from-the 1e 10 action mixture. 7

In testimony whereof, we aflix our signaturesfi" V f FRITZ BALLAUF;

ALBEB1$HMELZEB- 

